This invention relates to a combined oven which operates both on microwave heating and electric resistance heating and which further has a ventilating system as well as a device for the pyrolytic cleaning of the cooking chamber. The bottom of the cooking chamber is provided with a microwave window which is covered by a glass-ceramic plate and below which there are arranged a microwave connecting housing and devices for generating and guiding the microwave energy into the cooking chamber. The glass-ceramic plate is immobilized on the wall of the cooking chamber by means of a circumferential securing frame.
An oven of the above-outlined type is known and is disclosed, for example, in German Offenlegungsschrift (Laid-Open Application) No. 2,715,655. It is known that during cooking, particularly when effected by the conventional resistance heating unit, there is generated a substantial volume of vapor mist which contains in particular grease and egg white particles. From the cooking chamber, where a slight overpressure prevails, the vapor mist penetrates into the smallest cracks and openings in every place within the oven housing. As a result of a subsequent condensation of the vapor mist, components of the oven are soiled to a significant degree. In particular, the risk of such soiling is high regarding the electric or electronic components of the microwave generating apparatus and the waveguide which are practically inaccessible by the user. Consequently, the output of these components is adversely affected by such soiling precipitation and a premature breakdown of the apparatus can be expected.